Autoimmunity to the sodium-level sensor in the brain causes essential hypernatremia

Area of Science:

• Neuroscience
• Immunology
• Endocrinology

Background:

• The brain's sodium-level sensor, Na(x), is crucial for maintaining sodium homeostasis.
• Dysfunction in Na(x) signaling can lead to abnormal salt intake and fluid balance.

Observation:

• A patient presented with essential hypernatremia and autoantibodies targeting Na(x).
• The patient had a ganglioneuroma expressing Na(x), suggesting a paraneoplastic neurologic disorder.
• Tumor removal did not resolve the autoantibody levels or hypernatremia symptoms.

Findings:

• The patient's serum immunoglobulin fraction induced hypernatremia, altered water/salt intake, and diuresis in mice.
• Affected mice showed neuronal cell death, complement C3 deposits, and inflammation in Na(x)-expressing brain regions.

Implications:

• This study reveals a novel mechanism for hypernatremia pathogenesis linked to the Na(x) sodium-sensing system.
• It highlights the role of autoantibodies against Na(x) in paraneoplastic disorders affecting fluid balance.
• Findings offer new therapeutic targets for managing hypernatremia and related neurological conditions.